Biomass refers to renewable organic resources of biological origin, excluding fossil resources. In particular, cellulosic biomass is attracting attention. Being developed all over the world are technologies of degrading cellulose into saccharides and producing useful resources, such as alternatives for petroleum resources and biofuel, from the resulting saccharides by chemical conversion or fermentation technology using microorganisms.
Cellulosic biomass is mainly composed of cellulose, hemicellulose, and lignin. Such biomass is known to be degraded in a complicated form by synergistic action of, for example, a cellulase degrading cellulose and a hemicellulase degrading hemicellulose. Efficient utilization of cellulosic biomass needs to develop a saccharification enzyme capable of highly efficiently degrading cellulose and hemicellulose.
In order to efficiently degrade cellulose to glucose, the above-mentioned various cellulases are required to comprehensively function. In addition, since xylan is a polysaccharide which is contained in plants in a large amount next to cellulose, filamentous fungi, such as Trichoderma, producing various cellulases and xylanases have attracted attention as bacteria degrading plant saccharides (Non Patent Literature 1).
In particular, Trichoderma can simultaneously produce a cellulase and a xylanase and also produces a large amount of complexing enzymes thereof and has been therefore investigated as a host for cellulase production (Non Patent Literature 2).
However, in order to industrially produce a cellulase and a xylanase with filamentous fungi, it is necessary to develop a technology for inexpensive mass production and to produce a further productive strain.
For example, Avicel, which is microcrystalline cellulose, is generally used for production of cellulase, but it is expensive and is difficult to be used in industrial application from the viewpoint of cost. In addition, since many of cellulose substrates are insoluble, inexpensive and soluble carbon sources, such as glucose, are desirable to be used also from the viewpoint of load on the industrial process. However, culture using glucose is known to cause a reduction or saturation in productivity by a control mechanism called catabolite repression. It is known that, for example, in Aspergillus filamentous fungi, wide-area control transcription factors, such as CreA, CreB, CreC, and CreD, are involved in the catabolite repression (Patent Literatures 1 and 2). It is believed that the catabolite repression can be regulated by controlling these factors, but avoidance of glucose inhibition is conceived to be still insufficient. Mechanism analysis has been developed also in Trichoderma (Patent Literature 3 and Non Patent Literature 3), but many functionally unclear points still remain, and avoidance of glucose inhibition has not been achieved also in Trichoderma. 
Incidentally, a protein secreted by a filamentous fungus (mold) is also believed to be transferred from endoplasmic reticulum to cell membrane through the Golgi apparatus by secretory vesicles and then to the outside of the cell, as in other eukaryotic cells. The protein, such as a secreted enzyme, to be secreted to the outside of the cell first passes through the endoplasmic reticulum membrane while being synthesized on the endoplasmic reticulum membrane and is subjected to an appropriate folding or glycosylation in the endoplasmic reticulum. The protein then moves to the Golgi apparatus for further glycosylation and is then collected in secretory vesicles and is transferred cytoskeleton-dependently to the cell membrane. The protein is transferred by fusion of the secretory vesicles with the cell membrane and moves to the outside of the cell (Non Patent Literature 4). In order to correctly transfer a target protein, every process of the transfer is important, and the lack of the mechanism in each transport process can be an obstacle to the protein transport.
As one of gene expression control mechanisms using protein transport pathways, a transcription factor called sterol regulatory element binding protein (SREBP) is known. In an SREBP pathway regulating the gene expression of cholesterol synthesis enzymes, SREBP1 (also called Sre1 or SreA) forms a complex with an SREBP cleavage-activating protein and is transported from the endoplasmic reticulum to the Golgi apparatus. It is known that the SREBP is subjected to splicing on the Golgi apparatus as the destination and the activated SREBP remigrates into the nucleus to control the expression of the genes involved in a sterol synthesis pathway or a fatty acid or neutral lipid synthesis pathway (Non Patent Literature 5).
It has been reported that in fungi, the SREBP pathway is involved in pathogenicity or hypoxic response (Non Patent Literature 6), but the details thereof are not known. It has been recently reported that in Trichoderma, destruction of the SREBP pathway increases the productivity of a cellulase (Non Patent Literature 7), but the details of the relation between the SREBP pathway and the increase in the cellulase productivity are unclear.
[Patent Literature 1] JP-A-2014-168424
[Patent Literature 2] JP-A-2015-39349
[Patent Literature 3] JP-A-H11-512930
[Non Patent Literature]
[Non Patent Literature 1] Akihiko Kondo, Yoshihiko Amano, and Yutaka Tamaru, “Baiomasu Bunkai Koso Kenkyu no Saizensen (Research Frontier of Biomass Degrading Enzymes—Focused on Cellulases and Hemicellulases—”, CMC Publishing Co., Ltd. pp. 10-19
[Non Patent Literature 2] Wataru Ogasawara and Yosuke Shida, “Kagaku to Seibutsu (Chemistry and Biology)”, Vol. 50, The Japan Society for Bioscience, Biotechnology, and Agrochemistry, Vol. 50, No. 8, pp. 592-599, 2012, August
[Non Patent Literature 3] Amore A1, Giacobbe S, Faraco V., Curr Genomics, 2013, June, 14(4): 230-49
[Non Patent Literature 4] Saloheimo M1, Pakula T M., Microbiology, 2012, January, 158 (Pt 1): 46-57
[Non Patent Literature 5] Ryuichiro Sato, “Oleoscience 2001”, Vol. 1, No. 11, pp. 1065-1072
[Non Patent Literature 6] Clara M. Bien and Peter J. Espenshade, EUKARYOTIC CELL, 9(3), 352-359 (2010)
[Non Patent Literature 7] Dr. Lina Qin et al., “P63 Disruption of SREBP pathway results in hyper-secretion of cellulases in Filamentous fungi”, SIMB (Society for Industrial Microbiology & Biotechnology), Annual Meeting and Exhibition,
https://sim.confex.com/sim/2015/webprogram/Paper30506.htm l